Manage your subscription

Darwin missed ‘earliest’ Galapagos species

By Rowan Hooper

It is one of the most studied parts of the world, and played a major part in shaping Darwin’s thinking about the origin of species – yet the Galapagos Islands continue to give more to our understanding of biology.

It was finches that led Darwin to understand that species could change with environmental pressures, and now genetic analysis has revealed that a long-overlooked pink iguana is a species in its own right and may be one of the earliest examples of species diversification on the islands.

Galapagos land iguanas belong to the genus Conolophus, of which there are currently three recognised species. Remarkably, given their colour, pink iguanas were apparently not seen until they were noticed by park rangers in 1986. They are sometimes known as “rosada” iguanas, from the Spanish for pink.

Gabriele Gentile of Tor Vergata University of Rome, Italy, and colleagues took blood samples of rosada iguanas and the other two species in order to test their relatedness.

Advertisement

Already endangered

Genetic analysis shows that the rosada iguana originated in the Galapagos more than five million years ago, and diverged from the other land iguana populations even as the archipelago was still forming.

The species came into being even before the appearance of the Volcán Wolf volcano in the north of Isabela Island – the only place the rosada is now found.

The pink form, says Gentile, should be considered a third species, and is evolutionarily older than the other two species.

And though it has only recently been discovered, Gentile says conservation measures are needed to prevent the pink iguana from going extinct.

“Available data suggest that the population size of the pink iguana is very small,” he says. Feral cats in the region could be eating eggs and young iguanas, Gentile speculates. Direct hunting by humans is also blamed.

‘Good food’

Darwin spent five weeks exploring the Galapagos, but did not encounter the pink iguanas. We can assume, however, that he would not have been endeared to them.

Of the island’s famous marine iguanas, Darwin had this to say&colon; “hideous-looking creatures, of a dirty black colour, stupid and sluggish in their movements”, though he added in his diary that the animals swam “with perfect ease and swiftness”.

He didn’t think much of land iguanas either&colon; “hideous animals, but are considered good food”.